It protects a 1P+N final subcircuit at 230/240 V, 50 Hz, with a C-curve thermal-magnetic trip characteristic rated 20 A at 30 °C. The residual-current element is instantaneous-type (no intentional delay), so it trips without added time lag on earth faults. That dual rating means the device is certified for both residential-distribution boards and industrial panel applications where higher prospective fault currents are expected.
Temperature derating — what the 20 A rating actually delivers
The 20 A rating is valid at 30 °C ambient. At 40 °C the continuous current must be derated to 18.8 A; at 50 °C to 17.4 A; at 60 °C to 16.2 A; and at 70 °C to 14.6 A. These are per the manufacturer's published derating curve and are the values to use when sizing the RCBO in a warm enclosure — the 20 A nameplate is not the operating limit above 30 °C.
The 5SU1354-7KK20 occupies 2 modular width units (36 mm) on a DIN rail, with a depth of 77 mm (70 mm installation depth).